Glued structural elements of wood must have the appropriate mechanical properties. For wider application in practice, it is also important to improve their bending strength and rigidity. For this purpose, the mechanical properties of laminated veneer lumber (LVL) were improved with synthetic fibres, which were added into bonding layer of LVL. In the experiment, we used beech veneer, polyurethane and epoxy adhesives and synthetic fibres. We used carbon fibres, aramid and glass fibres. Reinforcement was added in the form of knitted nets in the two outer adhesives layers of the LVL and glued to the plate. The plate was then cut and experiments carried out to determine the modulus of elasticity using non-destructive and destructive methods. For the first technique we measured the speed of ultrasound along the specimens to determine dynamic modulus of elasticity, and followed by static mechanical three-point bending test. The greatest increase in the modulus of elasticity was achieved with adding of carbon fibres. The adhesive and fibre combinations have had different impacts on the improvements in bending stiffness and strength. The specimens glued with the polyurethane adhesive showed better strength properties than those made with epoxy adhesive. The more reinforcement fibres were used, the greater the stiffness of the tested specimens.